ChemWeb Newsletter

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This week the Alchemist discovers there may be no need for a magic bullet in cancer chemotherapy and a basic approach could be all that is needed. He also finds a smashing discovery that could explains glassy substances and precludes an ideal standard. Also in this week's issue, we learn that the ozone layer is finally on the mend, and hear about a co-polymer that not only fends of barnacles but can smell nice too. Finally, spontaneous chiral resolution with achiral ligands.

While global warming and climate change in general remain high on the scientific and political agendas, one of the more stubborn environmental problems of the last half century, the emergence of "holes" in the stratospheric ozone layer seems, at last, to be in reverse. The enforcement of 1987's Montreal Protocol, which was to ban the use and release of ozone-eating pollutants, seems to have had some impact, after all. However, according to NASA scientists, for the last 9 years, worldwide ozone has remained roughly constant, halting the decline first noticed in the 1980s. The hole above Antarctica remains a gaping maw, but the holes elsewhere in our atmosphere seem to be healing. Whether or not this is due to Montreal cannot be said with certainty because the ozone layer can also be affected by the weather, volcanic activity, and sunspots.

A material originally developed by US chemists for use as a marine "antifouling" coating has now been shown to capture fragrance molecules and release them at room temperature. The research team, led by Karen Wooley and James McDonnellv of Washington University in St. Louis say their polymeric material has a remarkable nanostructure that could be exploited for repelling pests, adding fragrance to the air or even as a nasal spray for administering certain drugs. Wooley fused two normally incompatible polymers - a hyperbranched fluoropolymer and a linear polyethylene glycol - let them phase-separate into distinct domains, one interspersed in the other and then cross-linked them to form the product. The resulting material is a heterogeneous, yet nanoscopically mountainous, coating with hydrophilic and hydrophobic ranges, in which barnacles cannot get a foothold. "We have these channels to serve as capillaries to take in guest molecules and hold them inside the material," explains Wooley, and as such guest fragrance molecules, or other species such as insect repellant or a drug, can be trapped by the materials and released subsequently under the right conditions.

It's the Holy Grail for many chemists - a solution to the problem of how to separate enantiomers, without using complicated chiral processes. Many have tried, many have failed, now we must hand it to Chinese researchers who claim to have cracked the chiral code. Chunying Duan and colleagues at Nanjing University observed spontaneous resolution of silver helicates without using any chiral additive. The key lies in the how the ligand bonds to the first metal center and passes on the chirality as the helix forms. C-H…pi and pi-pi stacking in the aromatic centers of the ligands result in only one handed form of the helicate forming and crystallizing.

Jeffrey Krise and colleagues at the University of Kansas at Lawrence have found a simple way to improve chemotherapy drugs, which works by making them basic. The new approach should allow anticancer drugs to accumulate in both normal and malignant cells, but be active only in the latter. The approach side-steps the issue of finding a magic bullet method of targeting cancer cells only and works because unlike healthy cells, cancer cells have an impaired ability to isolate and excrete basic substances, and so get hit with the full cytotoxic effect of the drug. "It could allow cancer patients to tolerate higher and more effective doses of chemotherapy before normal cells are damaged to an extent that causes serious side effects and cessation of therapy," Krise explains.

Princeton chemists have discovered that the formation of a glass always occurs differently depending on how quickly a liquid substance is cooled into its solid form. Researchers had suggested that an ideal glass passes through a transition point on cooling at which it snaps from disordered liquid into a solid-state order. Sal Torquato and colleagues at Princeton University performed a computer simulation of the transition and could see no well-defined transition point. The findings could have implications as far reaching as how to make better golf club heads and to understanding the structure of the early universe. Torquato explains, "Golf club heads made of metallic glasses, for example, can make golf balls fly farther. While our research could be utilized by industry, it can actually help us understand any 'glassy' multi-particle system, such as the early universe - which cosmologists have described as a glass." Their findings, published on June 6 in Physical Review Letters, also smash any chance of materials scientists finding the ideal glass.